DETROIT (AP)  Prosecutors dropped murder charges Wednesday against a man in the killing of a Detroit college police officer who was shot in the head while on duty, but did not elaborate on why they no longer consider him a suspect.

DeAngelo Davis” defense attorney said authorities lacked evidence and “dropped the ball” in their handling of the case.

Police and prosecutors say they”re committed to finding the person who shot Wayne State University officer Collin Rose on Nov. 22.

“As you can imagine, the officers from the homicide task force, including the Michigan State Police and the Detroit Police Department, have been working diligently and literally … around the clock, along with members of my office, on this case,” Wayne County Prosecutor Kym Worthy said at a news conference where she announced charges against Davis were being dropped. “We all remain deeply committed to making sure that justice is done in this case, making sure that the perpetrator for the killing of Officer Rose is brought to justice.”

Davis, 31, of Detroit, had been jailed without bond since his arrest the night of the shooting. He faced charges of first-degree murder and murder of a police officer. Worthy did not say why the charges were dropped and did not take any questions from reporters during the news conference.

In a statement after he was charged, Worthy said Davis was riding a bicycle when Rose stopped him. Rose was shot shortly after requesting help from other officers.

“The murder of Sgt. Rose was a tragic loss to the community and law enforcement, but it was also wrong to snatch Mr. DeAngelo Davis off the street and try this case in the media despite a lack of evidence connecting him to the crime,” James said. She went on to add that “in the case of Mr. Davis, law enforcement officials dropped the ball.”

James said Davis will speak publicly later.

Wayne State, which has more than 27,000 students, employs about 65 officers. Rose, 29, died a day after the shooting and was posthumously promoted to sergeant. He is the only Wayne State officer killed in the line of duty.

Detroit Police Chief James Craig said at the time that Rose was investigating possible thefts of navigation systems from vehicles. On Wednesday, he said “the investigation did not stop” despite Davis” arrest.